U.S. Pat. No. 5,409,134 to Cowger et al discloses an ink cartridge for an ink jet printer in which the back pressure within a sealed reservoir of the ink cartridge is regulated through an accumulator comprising a flexible bag mounted to a curved spring.
U.S. Pat. No. 5,526,030 to Baldwin et al has an air bubble generator for supplying air bubbles to a sealed reservoir to reduce its back pressure and a labyrinth for storing a predetermined volume of ink when the ink leaks through the air bubble generator.
U.S. Pat. No. 5,600,358 to Baldwin et al uses a hydrophobic membrane to prevent the flow of ink through an air vent opening connected to the labyrinth. Thus, the aforesaid Baldwin et al Patent, 5,600,358, recognizes the problem of ink leaking from the ink cartridge of the aforesaid Cowger et al patent. However, the aforesaid Baldwin et al patent, 5,600,358, requires the labyrinth and a second vent opening, which is connected to the labyrinth, adjacent the lowermost portion of the ink cartridge.